Multiple-stage gas generators with propellant charges which are able to be ignited independently of each other can generate different quantities of gas, coordinated with vehicle occupants or accident-specific parameters. If not all the propellant charges are ignited to achieve the optimum restraining effect, but only some of them, the outflowing hot gas, however, automatically heats the outer and inner walls, so that heat is passed on to the at least one non-ignited charge. Theoretically, this can lead to the self ignition of the non-ignited charge after a few minutes, due to the relatively slow transportation of heat. This involves dangers both for the occupant still situated in the vehicle, and also for rescue personnel.
Furthermore, a gas generator in which not all the stages are ignited represents a problem with regard to recycling/disposal. Generally it is not--at least not simply--possible to detect from the exterior, whether all the stages have been ignited, so that a recycling or a disposal of an activated gas generator will take an increased effort in terms of safety.